| Message ID | 20210617231948.2591431-3-dmatlack@google.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | KVM: x86/mmu: Clean up is_tdp_mmu_root and root_hpa checks | expand |
Hi David,
Thank you for the patch! Yet something to improve:
[auto build test ERROR on kvm/queue]
[also build test ERROR on vhost/linux-next v5.13-rc6]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch]
url: https://github.com/0day-ci/linux/commits/David-Matlack/KVM-x86-mmu-Remove-redundant-is_tdp_mmu_root-check/20210618-082018
base: https://git.kernel.org/pub/scm/virt/kvm/kvm.git queue
config: i386-randconfig-a016-20210618 (attached as .config)
compiler: gcc-9 (Debian 9.3.0-22) 9.3.0
reproduce (this is a W=1 build):
# https://github.com/0day-ci/linux/commit/6ab060f3cf9061da492b1eb89808eb2da5406781
git remote add linux-review https://github.com/0day-ci/linux
git fetch --no-tags linux-review David-Matlack/KVM-x86-mmu-Remove-redundant-is_tdp_mmu_root-check/20210618-082018
git checkout 6ab060f3cf9061da492b1eb89808eb2da5406781
# save the attached .config to linux build tree
make W=1 ARCH=i386
If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot <lkp@intel.com>
All errors (new ones prefixed by >>):
ld: arch/x86/kvm/mmu/mmu.o: in function `get_mmio_spte':
>> arch/x86/kvm/mmu/mmu.c:3612: undefined reference to `kvm_tdp_mmu_get_walk'
ld: arch/x86/kvm/mmu/mmu.o: in function `direct_page_fault':
>> arch/x86/kvm/mmu/mmu.c:3830: undefined reference to `kvm_tdp_mmu_map'
vim +3612 arch/x86/kvm/mmu/mmu.c
95fb5b0258b7bd arch/x86/kvm/mmu/mmu.c Ben Gardon 2020-10-14 3597
9aa418792f5f11 arch/x86/kvm/mmu/mmu.c Sean Christopherson 2020-12-17 3598 /* return true if reserved bit(s) are detected on a valid, non-MMIO SPTE. */
95fb5b0258b7bd arch/x86/kvm/mmu/mmu.c Ben Gardon 2020-10-14 3599 static bool get_mmio_spte(struct kvm_vcpu *vcpu, u64 addr, u64 *sptep)
95fb5b0258b7bd arch/x86/kvm/mmu/mmu.c Ben Gardon 2020-10-14 3600 {
dde81f9477d018 arch/x86/kvm/mmu/mmu.c Sean Christopherson 2020-12-17 3601 u64 sptes[PT64_ROOT_MAX_LEVEL + 1];
95fb5b0258b7bd arch/x86/kvm/mmu/mmu.c Ben Gardon 2020-10-14 3602 struct rsvd_bits_validate *rsvd_check;
39b4d43e6003ce arch/x86/kvm/mmu/mmu.c Sean Christopherson 2020-12-17 3603 int root, leaf, level;
95fb5b0258b7bd arch/x86/kvm/mmu/mmu.c Ben Gardon 2020-10-14 3604 bool reserved = false;
95fb5b0258b7bd arch/x86/kvm/mmu/mmu.c Ben Gardon 2020-10-14 3605
95fb5b0258b7bd arch/x86/kvm/mmu/mmu.c Ben Gardon 2020-10-14 3606 if (!VALID_PAGE(vcpu->arch.mmu->root_hpa)) {
95fb5b0258b7bd arch/x86/kvm/mmu/mmu.c Ben Gardon 2020-10-14 3607 *sptep = 0ull;
95fb5b0258b7bd arch/x86/kvm/mmu/mmu.c Ben Gardon 2020-10-14 3608 return reserved;
95fb5b0258b7bd arch/x86/kvm/mmu/mmu.c Ben Gardon 2020-10-14 3609 }
95fb5b0258b7bd arch/x86/kvm/mmu/mmu.c Ben Gardon 2020-10-14 3610
6ab060f3cf9061 arch/x86/kvm/mmu/mmu.c David Matlack 2021-06-17 3611 if (is_tdp_mmu_root(vcpu->arch.mmu->root_hpa))
39b4d43e6003ce arch/x86/kvm/mmu/mmu.c Sean Christopherson 2020-12-17 @3612 leaf = kvm_tdp_mmu_get_walk(vcpu, addr, sptes, &root);
95fb5b0258b7bd arch/x86/kvm/mmu/mmu.c Ben Gardon 2020-10-14 3613 else
39b4d43e6003ce arch/x86/kvm/mmu/mmu.c Sean Christopherson 2020-12-17 3614 leaf = get_walk(vcpu, addr, sptes, &root);
95fb5b0258b7bd arch/x86/kvm/mmu/mmu.c Ben Gardon 2020-10-14 3615
2aa078932ff6c6 arch/x86/kvm/mmu/mmu.c Sean Christopherson 2020-12-17 3616 if (unlikely(leaf < 0)) {
2aa078932ff6c6 arch/x86/kvm/mmu/mmu.c Sean Christopherson 2020-12-17 3617 *sptep = 0ull;
2aa078932ff6c6 arch/x86/kvm/mmu/mmu.c Sean Christopherson 2020-12-17 3618 return reserved;
2aa078932ff6c6 arch/x86/kvm/mmu/mmu.c Sean Christopherson 2020-12-17 3619 }
2aa078932ff6c6 arch/x86/kvm/mmu/mmu.c Sean Christopherson 2020-12-17 3620
9aa418792f5f11 arch/x86/kvm/mmu/mmu.c Sean Christopherson 2020-12-17 3621 *sptep = sptes[leaf];
9aa418792f5f11 arch/x86/kvm/mmu/mmu.c Sean Christopherson 2020-12-17 3622
9aa418792f5f11 arch/x86/kvm/mmu/mmu.c Sean Christopherson 2020-12-17 3623 /*
9aa418792f5f11 arch/x86/kvm/mmu/mmu.c Sean Christopherson 2020-12-17 3624 * Skip reserved bits checks on the terminal leaf if it's not a valid
9aa418792f5f11 arch/x86/kvm/mmu/mmu.c Sean Christopherson 2020-12-17 3625 * SPTE. Note, this also (intentionally) skips MMIO SPTEs, which, by
9aa418792f5f11 arch/x86/kvm/mmu/mmu.c Sean Christopherson 2020-12-17 3626 * design, always have reserved bits set. The purpose of the checks is
9aa418792f5f11 arch/x86/kvm/mmu/mmu.c Sean Christopherson 2020-12-17 3627 * to detect reserved bits on non-MMIO SPTEs. i.e. buggy SPTEs.
9aa418792f5f11 arch/x86/kvm/mmu/mmu.c Sean Christopherson 2020-12-17 3628 */
9aa418792f5f11 arch/x86/kvm/mmu/mmu.c Sean Christopherson 2020-12-17 3629 if (!is_shadow_present_pte(sptes[leaf]))
9aa418792f5f11 arch/x86/kvm/mmu/mmu.c Sean Christopherson 2020-12-17 3630 leaf++;
95fb5b0258b7bd arch/x86/kvm/mmu/mmu.c Ben Gardon 2020-10-14 3631
95fb5b0258b7bd arch/x86/kvm/mmu/mmu.c Ben Gardon 2020-10-14 3632 rsvd_check = &vcpu->arch.mmu->shadow_zero_check;
95fb5b0258b7bd arch/x86/kvm/mmu/mmu.c Ben Gardon 2020-10-14 3633
9aa418792f5f11 arch/x86/kvm/mmu/mmu.c Sean Christopherson 2020-12-17 3634 for (level = root; level >= leaf; level--)
b5c3c1b3c6e95c arch/x86/kvm/mmu/mmu.c Sean Christopherson 2020-01-09 3635 /*
b5c3c1b3c6e95c arch/x86/kvm/mmu/mmu.c Sean Christopherson 2020-01-09 3636 * Use a bitwise-OR instead of a logical-OR to aggregate the
b5c3c1b3c6e95c arch/x86/kvm/mmu/mmu.c Sean Christopherson 2020-01-09 3637 * reserved bit and EPT's invalid memtype/XWR checks to avoid
b5c3c1b3c6e95c arch/x86/kvm/mmu/mmu.c Sean Christopherson 2020-01-09 3638 * adding a Jcc in the loop.
b5c3c1b3c6e95c arch/x86/kvm/mmu/mmu.c Sean Christopherson 2020-01-09 3639 */
dde81f9477d018 arch/x86/kvm/mmu/mmu.c Sean Christopherson 2020-12-17 3640 reserved |= __is_bad_mt_xwr(rsvd_check, sptes[level]) |
dde81f9477d018 arch/x86/kvm/mmu/mmu.c Sean Christopherson 2020-12-17 3641 __is_rsvd_bits_set(rsvd_check, sptes[level], level);
47ab8751695f71 arch/x86/kvm/mmu.c Xiao Guangrong 2015-08-05 3642
47ab8751695f71 arch/x86/kvm/mmu.c Xiao Guangrong 2015-08-05 3643 if (reserved) {
bb4cdf3af9395d arch/x86/kvm/mmu/mmu.c Sean Christopherson 2021-02-25 3644 pr_err("%s: reserved bits set on MMU-present spte, addr 0x%llx, hierarchy:\n",
47ab8751695f71 arch/x86/kvm/mmu.c Xiao Guangrong 2015-08-05 3645 __func__, addr);
95fb5b0258b7bd arch/x86/kvm/mmu/mmu.c Ben Gardon 2020-10-14 3646 for (level = root; level >= leaf; level--)
bb4cdf3af9395d arch/x86/kvm/mmu/mmu.c Sean Christopherson 2021-02-25 3647 pr_err("------ spte = 0x%llx level = %d, rsvd bits = 0x%llx",
bb4cdf3af9395d arch/x86/kvm/mmu/mmu.c Sean Christopherson 2021-02-25 3648 sptes[level], level,
bb4cdf3af9395d arch/x86/kvm/mmu/mmu.c Sean Christopherson 2021-02-25 3649 rsvd_check->rsvd_bits_mask[(sptes[level] >> 7) & 1][level-1]);
47ab8751695f71 arch/x86/kvm/mmu.c Xiao Guangrong 2015-08-05 3650 }
ddce6208217c1a arch/x86/kvm/mmu/mmu.c Sean Christopherson 2019-12-06 3651
47ab8751695f71 arch/x86/kvm/mmu.c Xiao Guangrong 2015-08-05 3652 return reserved;
ce88decffd17bf arch/x86/kvm/mmu.c Xiao Guangrong 2011-07-12 3653 }
ce88decffd17bf arch/x86/kvm/mmu.c Xiao Guangrong 2011-07-12 3654
---
0-DAY CI Kernel Test Service, Intel Corporation
https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org
On 18/06/21 09:17, kernel test robot wrote: > Hi David, > > Thank you for the patch! Yet something to improve: > > [auto build test ERROR on kvm/queue] > [also build test ERROR on vhost/linux-next v5.13-rc6] > [If your patch is applied to the wrong git tree, kindly drop us a note. > And when submitting patch, we suggest to use '--base' as documented in > https://git-scm.com/docs/git-format-patch] > > url:https://github.com/0day-ci/linux/commits/David-Matlack/KVM-x86-mmu-Remove-redundant-is_tdp_mmu_root-check/20210618-082018 > base:https://git.kernel.org/pub/scm/virt/kvm/kvm.git queue > config: i386-randconfig-a016-20210618 (attached as .config) > compiler: gcc-9 (Debian 9.3.0-22) 9.3.0 > reproduce (this is a W=1 build): > #https://github.com/0day-ci/linux/commit/6ab060f3cf9061da492b1eb89808eb2da5406781 > git remote add linux-reviewhttps://github.com/0day-ci/linux > git fetch --no-tags linux-review David-Matlack/KVM-x86-mmu-Remove-redundant-is_tdp_mmu_root-check/20210618-082018 > git checkout 6ab060f3cf9061da492b1eb89808eb2da5406781 > # save the attached .config to linux build tree > make W=1 ARCH=i386 > > If you fix the issue, kindly add following tag as appropriate > Reported-by: kernel test robot<lkp@intel.com> > > All errors (new ones prefixed by >>): > > ld: arch/x86/kvm/mmu/mmu.o: in function `get_mmio_spte': >>> arch/x86/kvm/mmu/mmu.c:3612: undefined reference to `kvm_tdp_mmu_get_walk' > ld: arch/x86/kvm/mmu/mmu.o: in function `direct_page_fault': >>> arch/x86/kvm/mmu/mmu.c:3830: undefined reference to `kvm_tdp_mmu_map' Turns out sometimes is_tdp_mmu_root is not inlined after this patch. Fixed thusly: --------- 8< ----------- Subject: [PATCH] KVM: x86: Stub out is_tdp_mmu_root on 32-bit hosts If is_tdp_mmu_root is not inlined, the elimination of TDP MMU calls as dead code might not work out. To avoid this, explicitly declare the stubbed is_tdp_mmu_root on 32-bit hosts. Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> diff --git a/arch/x86/kvm/mmu/tdp_mmu.h b/arch/x86/kvm/mmu/tdp_mmu.h index fabfea947e46..f6e0667cf4b6 100644 --- a/arch/x86/kvm/mmu/tdp_mmu.h +++ b/arch/x86/kvm/mmu/tdp_mmu.h @@ -85,12 +85,6 @@ bool kvm_mmu_init_tdp_mmu(struct kvm *kvm); void kvm_mmu_uninit_tdp_mmu(struct kvm *kvm); static inline bool is_tdp_mmu_enabled(struct kvm *kvm) { return kvm->arch.tdp_mmu_enabled; } static inline bool is_tdp_mmu_page(struct kvm_mmu_page *sp) { return sp->tdp_mmu_page; } -#else -static inline bool kvm_mmu_init_tdp_mmu(struct kvm *kvm) { return false; } -static inline void kvm_mmu_uninit_tdp_mmu(struct kvm *kvm) {} -static inline bool is_tdp_mmu_enabled(struct kvm *kvm) { return false; } -static inline bool is_tdp_mmu_page(struct kvm_mmu_page *sp) { return false; } -#endif static inline bool is_tdp_mmu_root(hpa_t hpa) { @@ -105,5 +99,12 @@ static inline bool is_tdp_mmu_root(hpa_t hpa) return is_tdp_mmu_page(sp) && sp->root_count; } +#else +static inline bool kvm_mmu_init_tdp_mmu(struct kvm *kvm) { return false; } +static inline void kvm_mmu_uninit_tdp_mmu(struct kvm *kvm) {} +static inline bool is_tdp_mmu_enabled(struct kvm *kvm) { return false; } +static inline bool is_tdp_mmu_page(struct kvm_mmu_page *sp) { return false; } +static inline bool is_tdp_mmu_root(hpa_t hpa) { return false; } +#endif #endif /* __KVM_X86_MMU_TDP_MMU_H */
On Fri, Jun 18, 2021 at 12:42:56PM +0200, Paolo Bonzini wrote: > On 18/06/21 09:17, kernel test robot wrote: > > Hi David, > > > > Thank you for the patch! Yet something to improve: > > > > [auto build test ERROR on kvm/queue] > > [also build test ERROR on vhost/linux-next v5.13-rc6] > > [If your patch is applied to the wrong git tree, kindly drop us a note. > > And when submitting patch, we suggest to use '--base' as documented in > > https://git-scm.com/docs/git-format-patch] > > > > url:https://github.com/0day-ci/linux/commits/David-Matlack/KVM-x86-mmu-Remove-redundant-is_tdp_mmu_root-check/20210618-082018 > > base:https://git.kernel.org/pub/scm/virt/kvm/kvm.git queue > > config: i386-randconfig-a016-20210618 (attached as .config) > > compiler: gcc-9 (Debian 9.3.0-22) 9.3.0 > > reproduce (this is a W=1 build): > > #https://github.com/0day-ci/linux/commit/6ab060f3cf9061da492b1eb89808eb2da5406781 > > git remote add linux-reviewhttps://github.com/0day-ci/linux > > git fetch --no-tags linux-review David-Matlack/KVM-x86-mmu-Remove-redundant-is_tdp_mmu_root-check/20210618-082018 > > git checkout 6ab060f3cf9061da492b1eb89808eb2da5406781 > > # save the attached .config to linux build tree > > make W=1 ARCH=i386 > > > > If you fix the issue, kindly add following tag as appropriate > > Reported-by: kernel test robot<lkp@intel.com> > > > > All errors (new ones prefixed by >>): > > > > ld: arch/x86/kvm/mmu/mmu.o: in function `get_mmio_spte': > > > > arch/x86/kvm/mmu/mmu.c:3612: undefined reference to `kvm_tdp_mmu_get_walk' > > ld: arch/x86/kvm/mmu/mmu.o: in function `direct_page_fault': > > > > arch/x86/kvm/mmu/mmu.c:3830: undefined reference to `kvm_tdp_mmu_map' > > Turns out sometimes is_tdp_mmu_root is not inlined after this patch. > Fixed thusly: Thanks for the fix. I guess after I removed the is_tdp_mmu_enabled() check the compiler couldn't determine what is_tdp_mmu_root() would return on 32-bit builds anymore. Pretty nice of the compiler to throw out kvm_tdp_mmu_get_walk() and kvm_tdp_mmu_map() once it knows they are not reachable so we don't have to implement stubs for those functions that BUG_ON and pray they never get called! > > --------- 8< ----------- > Subject: [PATCH] KVM: x86: Stub out is_tdp_mmu_root on 32-bit hosts > > If is_tdp_mmu_root is not inlined, the elimination of TDP MMU calls as dead > code might not work out. To avoid this, explicitly declare the stubbed > is_tdp_mmu_root on 32-bit hosts. > > Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> > > diff --git a/arch/x86/kvm/mmu/tdp_mmu.h b/arch/x86/kvm/mmu/tdp_mmu.h > index fabfea947e46..f6e0667cf4b6 100644 > --- a/arch/x86/kvm/mmu/tdp_mmu.h > +++ b/arch/x86/kvm/mmu/tdp_mmu.h > @@ -85,12 +85,6 @@ bool kvm_mmu_init_tdp_mmu(struct kvm *kvm); > void kvm_mmu_uninit_tdp_mmu(struct kvm *kvm); > static inline bool is_tdp_mmu_enabled(struct kvm *kvm) { return kvm->arch.tdp_mmu_enabled; } > static inline bool is_tdp_mmu_page(struct kvm_mmu_page *sp) { return sp->tdp_mmu_page; } > -#else > -static inline bool kvm_mmu_init_tdp_mmu(struct kvm *kvm) { return false; } > -static inline void kvm_mmu_uninit_tdp_mmu(struct kvm *kvm) {} > -static inline bool is_tdp_mmu_enabled(struct kvm *kvm) { return false; } > -static inline bool is_tdp_mmu_page(struct kvm_mmu_page *sp) { return false; } > -#endif > static inline bool is_tdp_mmu_root(hpa_t hpa) > { > @@ -105,5 +99,12 @@ static inline bool is_tdp_mmu_root(hpa_t hpa) > return is_tdp_mmu_page(sp) && sp->root_count; > } > +#else > +static inline bool kvm_mmu_init_tdp_mmu(struct kvm *kvm) { return false; } > +static inline void kvm_mmu_uninit_tdp_mmu(struct kvm *kvm) {} > +static inline bool is_tdp_mmu_enabled(struct kvm *kvm) { return false; } > +static inline bool is_tdp_mmu_page(struct kvm_mmu_page *sp) { return false; } > +static inline bool is_tdp_mmu_root(hpa_t hpa) { return false; } > +#endif > #endif /* __KVM_X86_MMU_TDP_MMU_H */ >
On 18/06/21 18:47, David Matlack wrote: > On Fri, Jun 18, 2021 at 12:42:56PM +0200, Paolo Bonzini wrote: >> On 18/06/21 09:17, kernel test robot wrote: >>> ld: arch/x86/kvm/mmu/mmu.o: in function `get_mmio_spte': >>>>> arch/x86/kvm/mmu/mmu.c:3612: undefined reference to `kvm_tdp_mmu_get_walk' >>> ld: arch/x86/kvm/mmu/mmu.o: in function `direct_page_fault': >>>>> arch/x86/kvm/mmu/mmu.c:3830: undefined reference to `kvm_tdp_mmu_map' >> >> Turns out sometimes is_tdp_mmu_root is not inlined after this patch. >> Fixed thusly: > > Thanks for the fix. I guess after I removed the is_tdp_mmu_enabled() > check the compiler couldn't determine what is_tdp_mmu_root() would > return on 32-bit builds anymore. It still could, but only as long as is_tdp_mmu_root was inlined. Your patch caused the final "return false" to only appear after a few WARN_ON checks that obviously can't be removed, and therefore tipped the balance towards not inlining it! Paolo
diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c index 0144c40d09c7..1e6bf2e207f6 100644 --- a/arch/x86/kvm/mmu/mmu.c +++ b/arch/x86/kvm/mmu/mmu.c @@ -3545,7 +3545,7 @@ static bool get_mmio_spte(struct kvm_vcpu *vcpu, u64 addr, u64 *sptep) return reserved; } - if (is_tdp_mmu_root(vcpu->kvm, vcpu->arch.mmu->root_hpa)) + if (is_tdp_mmu_root(vcpu->arch.mmu->root_hpa)) leaf = kvm_tdp_mmu_get_walk(vcpu, addr, sptes, &root); else leaf = get_walk(vcpu, addr, sptes, &root); @@ -3717,6 +3717,7 @@ static bool try_async_pf(struct kvm_vcpu *vcpu, bool prefault, gfn_t gfn, static int direct_page_fault(struct kvm_vcpu *vcpu, gpa_t gpa, u32 error_code, bool prefault, int max_level, bool is_tdp) { + bool is_tdp_mmu_fault = is_tdp_mmu_root(vcpu->arch.mmu->root_hpa); bool write = error_code & PFERR_WRITE_MASK; bool map_writable; @@ -3729,7 +3730,7 @@ static int direct_page_fault(struct kvm_vcpu *vcpu, gpa_t gpa, u32 error_code, if (page_fault_handle_page_track(vcpu, error_code, gfn)) return RET_PF_EMULATE; - if (!is_tdp_mmu_root(vcpu->kvm, vcpu->arch.mmu->root_hpa)) { + if (!is_tdp_mmu_fault) { r = fast_page_fault(vcpu, gpa, error_code); if (r != RET_PF_INVALID) return r; @@ -3751,7 +3752,7 @@ static int direct_page_fault(struct kvm_vcpu *vcpu, gpa_t gpa, u32 error_code, r = RET_PF_RETRY; - if (is_tdp_mmu_root(vcpu->kvm, vcpu->arch.mmu->root_hpa)) + if (is_tdp_mmu_fault) read_lock(&vcpu->kvm->mmu_lock); else write_lock(&vcpu->kvm->mmu_lock); @@ -3762,7 +3763,7 @@ static int direct_page_fault(struct kvm_vcpu *vcpu, gpa_t gpa, u32 error_code, if (r) goto out_unlock; - if (is_tdp_mmu_root(vcpu->kvm, vcpu->arch.mmu->root_hpa)) + if (is_tdp_mmu_fault) r = kvm_tdp_mmu_map(vcpu, gpa, error_code, map_writable, max_level, pfn, prefault); else @@ -3770,7 +3771,7 @@ static int direct_page_fault(struct kvm_vcpu *vcpu, gpa_t gpa, u32 error_code, prefault, is_tdp); out_unlock: - if (is_tdp_mmu_root(vcpu->kvm, vcpu->arch.mmu->root_hpa)) + if (is_tdp_mmu_fault) read_unlock(&vcpu->kvm->mmu_lock); else write_unlock(&vcpu->kvm->mmu_lock); diff --git a/arch/x86/kvm/mmu/tdp_mmu.h b/arch/x86/kvm/mmu/tdp_mmu.h index 5fdf63090451..843ca2127faf 100644 --- a/arch/x86/kvm/mmu/tdp_mmu.h +++ b/arch/x86/kvm/mmu/tdp_mmu.h @@ -91,12 +91,10 @@ static inline bool is_tdp_mmu_enabled(struct kvm *kvm) { return false; } static inline bool is_tdp_mmu_page(struct kvm_mmu_page *sp) { return false; } #endif -static inline bool is_tdp_mmu_root(struct kvm *kvm, hpa_t hpa) +static inline bool is_tdp_mmu_root(hpa_t hpa) { struct kvm_mmu_page *sp; - if (!is_tdp_mmu_enabled(kvm)) - return false; if (WARN_ON(!VALID_PAGE(hpa))) return false;
This check is redundant because the root shadow page will only be a TDP MMU page if is_tdp_mmu_enabled() returns true, and is_tdp_mmu_enabled() never changes for the lifetime of a VM. It's possible that this check was added for performance reasons but it is unlikely that it is useful in practice since to_shadow_page() is cheap. That being said, this patch also caches the return value of is_tdp_mmu_root() in direct_page_fault() since there's no reason to duplicate the call so many times, so performance is not a concern. Suggested-by: Sean Christopherson <seanjc@google.com> Signed-off-by: David Matlack <dmatlack@google.com> --- arch/x86/kvm/mmu/mmu.c | 11 ++++++----- arch/x86/kvm/mmu/tdp_mmu.h | 4 +--- 2 files changed, 7 insertions(+), 8 deletions(-)